Multi-layered polymer preform and container via selective heat up additives

ABSTRACT

A multilayered polymeric preform or container is disclosed wherein the blow temperatures of each polymer in a preform is controlled by the addition of a predetermined selected amount of a fast heat up additive such that each polymer layer blows at the same relative period of time to prepare the container.

FIELD OF THE INVENTION

This invention relates to a preform and container and a method to makesaid preform and container by providing at least two polymeric layerswith different blowing temperatures, wherein at least one additive ispresent. The additive(s) exist in quantities sufficient to cause thepolymeric layers to heat to their respective blow temperatures in thesame or essentially the same period of time.

BACKGROUND OF THE INVENTION

Energy absorbing materials such as carbon black and graphite have beenused in polymeric materials to reduce heat up time. Pengilly, U.S. Pat.No. 4,408,004 discloses the use of carbon black in PET in a range fromless than 10 parts per million (ppm). The carbon black can be added atany stage of the polyester preparation, such as the esterification orthe transesterification reaction or at the condensation stage. TheExample of the '004 patent show that the carbon black can be added incontrolled quantities such that the polymer heats up faster but stillproduces a high clarity, low haze polymer.

Laser imageable assemblies comprising transparent material have calledfor the use of carbon black and/or graphite as energy absorbingmaterial. In U.S. Pat. No. 4,711,834, a disclosure is made to usegraphite and carbon black in a binder resin in amounts such that theweight ratio of particles to binder resin is 10:1 to 1:2. The polymericmaterial discussed includes the terephthalic acid and the 2,6 (NDC is2,6, but some work does contemplate 2,7) -naphthalene dicarboxylic acid,each combined with ethylene glycol. These energy-absorbing materials aredispersed in the heterogeneous resin layer to absorb energy passingthrough the layer.

Containers, most specifically bottles, have been developed to hold foodand beverages comprised of polymeric materials such as PET and PEN. Theart also indicates that both PEN and PET layered bottles can be used toattain the benefits of some of the barrier properties of the PEN withthe cost efficiency of the PET. Other disclosures have lined thesepolymers with substrates such as aluminum or glass to also achieve highbarrier, low cost properties.

While these concepts have been disclosed for PEN and PET, no successfulbottle has been made from the strain hardenable versions because of thesignificant difference in blowing temperature of PEN and PET. When oneheats that multi-layer structure at the same rate, the PEN is either toocold to blow or the PET is too hot to blow. This problem was describedin 1994. (Excerpt from BevPak Americas 1994, Sisson, Callander, “HighPerformance PEN & Naphthalate Based Packaging Resins”, Presented Apr.11, 1994.)

“. . . Tg's and melt points have a “linear function”.

This is important, particularly for those interested in co-injection ormultilayer structures. Previous work with PEN homopolymer/PET structuresindicates that the melt points and the Tgs of the PEN and PEThomopolymers were too far apart for a two step process. In the injectionstep, the heat required to melt the PEN would crystallize the PET and inthe reheat step, the temperature required to reach PENs Tg was too greatfor the PET.”

Some art discloses PEN as an example of an inner layer. However, the PENdescribed is a highly modified copolymer such that is not strainhardenable. It has no melting point or crystalline type conditions. Thislimits this art to the properties of an essentially amorphous PEN withsubstantially less naphthalate. In addition to not maximizing theproperties for the amount of PEN, the amorphous materials are costly todry and process relative to a crystalline material.

The problem addressed in this invention is the fact that multilayers ofPEN/PET polymers cannot be reheat blown with traditional formulations.Recognition is made of the difference in the T_(g) values between PENand PET. This large difference creates two separate blow windows whichdo not overlap and has thus made it difficult to make a multilayerPET/PEN bottle using a reheat blow process from a preform.

This invention provides substantial improvements over the art. Bychanging the heating rate of the PEN (or PET or both) so that it or theyreaches its higher blow temperature at the same time the PET reaches itslower blow temperature, one can now incorporate crystallizable andstrain hardenable PEN's and their advantages of orientation andprocessing.

SUMMARY OF INVENTION

This invention describes a multilayer polymeric preform or containerwherein the blow temperatures of each polymer layer is controlled by theaddition of a faster heat up rate additives such that the polymer layersin the preforms blow at the same relative period of time to make thecontainer.

DETAILED DESCRIPTION OF THE INVENTION

This invention encompasses a multilayered polymeric preform and/orcontainer. The container blown from the preform is preferably a beveragebottle useful for containing liquids such as beer or soft drinks. In thepreforms, it is important to have the high barrier properties of PENcombined with the low cost of PET to form an economically viable bottle.

PET can be made from the polycondensation reaction of terephthalic acidor its ester and ethylene glycol or other similar diol. PEN can be madefrom the reaction of napthalene dicarboxylic acids, or its ester, withethylene glycol or another type of diol.

It is also considered within the scope of this invention that the PENand the PET substrates may be copolymers of PEN or PET within theconventional knowledge of the copolymers of these materials. The PET andPEN are preferably a strain hardenable or crystallizable variant.

It is necessary to heat the preforms in order to make the blown bottlesfor use with the beverage. The preform is heated by infrared lamps whichabsorb energy over a period of time. It is advantageous if this periodof time can be reduced as much as possible to save energy and time.

It has now been discovered that a preform can be produced containingmultiple layers of polymers, particularly PET and PEN which can be madeto heat up at the same time. This invention provides for the selectiveand pre-determined addition of fast heat up additives so that the PENand PET layers are preferentially heated to a proper blow temperature atdifferent rates but will reach a final polymeric blow temperature at thesame or substantially the same time. This is done by tailoring theindividual layers by using the additive or faster heat up component inthe PEN layer and if desired, some slower heat up or slowercrystallizing component in the PET layer. By doing this, both layersreach their respective blow temperatures in their respective blow windowat the same or substantially the same time.

The blowing process is not usually a single temperature, but isdescribed by those skilled in the art as the blow window. The blowwindow exists over a temperature range. It is different for eachpolymer. Blowing the preform outside the blow window results in poorcontainer shape, pearlessance and/or white crystallinity; depending uponwhich side of the blow window the preform is blown.

The fast heat up additive material charged to the respective polymericlayers will comprise either different colorants or other heat upmaterials, such as carbon black and/or graphite and/or diamond dust. Thequantity of colorant and/or various forms of carbon will be present inthe PET or the PEN at approximately 5 ppm to about 1000 ppm. It isimportant to pre-calculate or pre-determine the amount of heat upmaterial additives necessary to add to the layers of the preform wherebythe respective PEN and the PET layers will consume the same amount oftime to form the blown bottle container from the preform. The thicknessof the layers, the composition and clarity of the polymers, and whetheror not the layers will be interior or exterior of one another may varythe predetermined amount of fast heat up additive such that no empiricalamount can be recited.

It is contemplated within the scope of this invention that the PET maybe used on the interior of the bottle with respect to the inside of thebottle or on the outside of the bottle. When the PET is used on theoutside of the bottle, the PEN is then used on the inside of the bottle,in contact with the beverage. Likewise when the PEN is used on theoutside of the bottle, the PET may be used on the inside of the bottlein contact with the beverage. Also contemplated is an A/B/A structurewhere A is PEN and B is PET or vice versa. It is also contemplated thatmultiple layers of other polymers may be used such as polybutylene orIPA modified copolymers of PET. It is important that these layersconfigure to demonstrate reheat process at the same time.

While the examples here use PEN and PET, the solution is applicable toother systems where the polymer blow temperatures are different.

EXAMPLES

A PEN material sold under the trademark as HiPERTUF™ 90000 was producedusing a Nissei 52 injection unit. Different colorants were also providedand added to the PEN. The colorants are typically found in colorantssupplied by Color Matrix. There were two yellows, a red, blue, tan andtwo blacks that were evaluated for heat up rates. Each of the sevencolors was evaluated at 2 (LDR) for a total of 14 hours. The preformswere injected using standard Nissei 16-ounce molds. The followingformula was used to calculate the pump setting over each run:${Ps} = \frac{{Shot}\quad {size} \times \# \quad {cavities} \times {LDR} \times {Constant}}{d_{1}}$$\begin{matrix}{where} \\{{Ps} = {{Pump}\quad {setting}}} \\{{{Shot}\quad {size}} = {28.7\quad g}} \\{{\# \quad {cavities}} = 1} \\{{LDR} = {{{Let}\quad {Down}\quad {Ratio}} = {0.05\quad {minimum}\quad {and}\quad 0.10\quad {maximum}\quad {for}}}} \\{{all}\quad {colors}\quad {except}\quad \tan \quad {and}\quad {black}\quad 1\quad {LDR}\quad {for}\quad {Tan}\quad {was}\quad 0.036\quad \left( \min \right)} \\{{and}\quad 0.055\quad \left( \max \right)} \\{{Constant} = {1.35 \times 6.6\quad \left( {{based}\quad {on}\quad {pump}} \right)}} \\{d_{1} = {{Density}\quad {of}\quad {liquid}\quad {colorant}}}\end{matrix}$

where the individual colors were evaluated and shown in Table 1.

TABLE 1 Pump Pump Density LDR LDR Setting Setting Colorant Color (min)(max) (min) (max) (lb/gal) Yellow 1 0.05 0.10 1.5 3.0 8.52 Yellow 2 0.050.10 1.6 3.2 8.03 Red 0.05 0.10 1.3 2.6 9.75 Blue 0.05 0.10 1.5 3.0 8.10Tan 0.036 0.055 1.0 1.5 9.28 Black 1 0.034 0.049 1.0 1.5 8.73 Black 20.05 0.10 1.6 3.2 7.84

Heat up rates of the colors were determined by reheating the preforms onthe RHBO-L equipment using IR cameras and Prism DS by FSI to measure thetemperature of the preforms just prior to the mold close. Preformtemperatures were determined across the entire blow window for eachcolor's pearlesscence. FIG. 1 shows the heat up rates for each additive.This showing indicates that the black colors heat up on an order of 1.5times faster than the other colors. This color is usually present wherecarbon black has been used.

From this showing, the heat up rates of a PEN/PET multilayered containermay be tailored so that the slower heating components in a slowcrystallizing PET formulation would finish their reheat process at thesame time as the PEN layer having the same or different additivematerials in the same or different quantity. By doing this, both layersreach their respective blow temperatures in essentially the same amountof time.

EXAMPLE 2

A demonstration of this technique was accomplished by creating a preformhaving a 1 mm inner layer of PEN with a faster heating amber colorant.The outer layer was a PET copolymer of 3 mm thickness. The preforms weresuccessfully blown into bottles without pearlessance.

What is claimed as our invention is:
 1. A preform comprised of multiplepolymer layers, each polymer layer having a blow window for blowing acontainer, wherein at least one polymeric layer has an amount of fastheat up additive effective for essentially equalizing heating timesrequired for the individual polymeric layers to reach their respectiveblow windows.
 2. The preform of claim 1 wherein one polymeric layercomprises polyethylene naphthalate (PEN) and a second layer comprisespolyethylene terephthalate (PET).
 3. The preform of claim 1 wherein thefast heat up additive comprises a compound selected from the groupconsisting of carbon black, graphite, diamond dust and combinationsthereof.
 4. The preform of claim 1 wherein the fast heat up additivecomprises a colorant composition.
 5. The preform of claim 2 wherein thePEN is external and the PET is internal with respect to an interior ofthe preform.
 6. The preform of claim 2 wherein the PET is external andthe PEN is internal with respect to an interior of the preform.
 7. Thepreform of claim 1 wherein the preform is a beverage bottle preform. 8.A bottle made from the preform of claim 7 wherein the bottle haspolymeric layers which act as barriers for said beverage.
 9. A method ofmaking a bottle preform having multiple polymeric layers, the methodcomprising: a) forming a first layer of polymeric material as one layerof the preform; and b) forming a second layer of polymeric material,juxtaposed to said first layer of polymeric material, wherein apredetermined amount of at least one fast heat up additive has beenadded to at least one polymeric layer in quantities sufficient to causethe first and second polymeric layers to heat to their respective blowtemperatures in the same or essentially the same period of time; and c)heating said bottle preform to blow temperatures.
 10. The process ofclaim 9 wherein the first layer of polymeric material is selected fromthe group consisting of PET and PEN and wherein, when the first layer ischosen to be PET, the second layer is chosen to be PEN and when thefirst layer is chosen to be PEN the second layer is chosen to be PET.11. The process of claim 10 wherein the respective PET or PEN chosen asthe first and second layer is a strain hardenable crystallizable variantof the PEN or PET or both.
 12. The process of claim 9 wherein the fastheat up additive comprises a compound selected from the group consistingof carbon black, graphite, diamond dust, colorant compositions andcombinations thereof.
 13. The process of claim 12 wherein the fast heatup additive is present in a quantity of 5 ppm to 1000 ppm.
 14. Theprocess of claim 9 wherein the preform comprises a beverage bottlecontainer wherein said respective blow temperatures are reached at thesame or essentially the same period of time.